High oxygen oxidant is being increasingly employed in carrying out combustion in industrial furnaces such as steelmaking furnaces and aluminum making furnaces. High oxygen oxidant is a mixture comprising at least 30 volume percent oxygen and preferably comprising at least 80 volume percent oxygen. High oxygen oxidant also includes commercially pure oxygen which has an oxygen concentration of 99.5 volume percent or more. Combustion carried out with high oxygen oxidant is more fuel efficient than combustion carried out with air because much less energy is used to process and heat nitrogen which comprises nearly 80 volume percent of air. Moreover, combustion carried out with high oxygen oxidant has environmental advantages because less nitrogen is available to the combustion reaction to react with oxygen to form nitrogen oxides (NOx) which are considered to be significant environmental pollutants.
Combustion carried out with high oxygen oxidant is generally characterized by a higher combustion reaction temperature than would be the case if air were used as the oxidant. The high combustion reaction temperature can damage or reduce the life of the burner nozzle. Moreover, these higher combustion temperatures produce a large percentage of free radicals such as O, OH and H, in the flame zone. If these free radicals come in contact with a surface, they recombine and release significant amounts of heat in the process. If the burner nozzle does not have adequate heat removal, it can be overheated and damaged which could reduce the life of the nozzle.
One way to reduce such burner nozzle damage is to cool the burner and the nozzle with water or some other liquid coolant. However, such water cooling is complicated to carry out, increases the possibility of corrosion of burner parts, and raises the danger that the water could leak and damage the furnace and the furnace charge such as steel, aluminum, etc.
Accordingly it is an object of this invention to provide an oxidant injector or lance for a burner which can operate with high oxygen oxidant and which does not require the use of water cooling to avoid damage to the burner nozzle.
It is another object of this invention to provide a combustion method which can employ high oxygen oxidant without the need for water cooling the oxidant injection nozzle.